I have the 52 qt version of that pot, and it works great. Not flimsy at all. The nice thing about it (besides price) is that the steamer rack which is included works great to keep your bag off the bottom, if you biab. If you mash in a tun, just don't use the rack of course.
I'm actually picking up that pot tonight for a co-worker who I just got into homebrewing.
Don't worry about aluminum, it poses NO PROBLEMS! Stainless is nice, but if cost is an issue aluminum is great. If aluminum posed issues, restaurants all over the place wouldn't be allowed to use it, especially in the crazy cancer-awareness state of CA, so keep that in mind.